In the US what happens is the card company says to Bob's Hardware, you must accept all our cards or you can't accept any cards, and our "Premium Reward" card has 7% interchange fee so when Jimmy presents his "Premium Reward" card for a $1000 purchase, the card company takes $70 of that. Jimmy gets $50 and he think he's a genius for having this card. The hardware store needs to raise prices for all customers to allow for people like Jimmy. So when Sarah, whose crappy job barely is enough to live on buys a product that would be $500 the store charges $540. Sarah's card only has an interchange fee of $10 and Sarah gets none of that, but the shop owner is legally prohibited from charging Jimmy more than Sarah and they're legally prohibited from refusing Jimmy's card unless they also refuse Sarah's.